In the processing of textiles it is a common practice to use chemicals and processing techniques to affect the fabric's physical and chemical characteristics. An excellent summary of textile processing techniques is provided in TEXTILE TECHNOLOGY, Encyclopedia Of Chemical Technology, Edited by R. E. Kirk & D. F. Othmer, 13, 856-907 (1954). The garment industry uses chemicals and processing techniques commonly referred to in the industry as "finishing," to achieve garment characteristics which are desired by the consumer. Commonly, these characteristics relate to the appearance, washability or softness of the garment. For example, U.S. Pat. No. 4,218,220 to Kappler et al. discloses a process for treating blue jeans to obtain a pre-faded appearance, by subjecting the garments to a washing cycle using bleach, fabric softener and detergent. U.S. Pat. No. 4,575,887 to Viramontes discloses a process for washing garments with abrasive particles for a "stone-washed" appearance. Typically these treatment steps are carried out as immersion processes in conventional, industrial two-drum washing machines such as, for example, a UniMac rotary, front-loading type washer, or in a single drum fabric finishing machine such as that disclosed in U.S. Pat. No. 4,941,333 to Blessing.
A "stone-washed" appearance of denim garments is of particular interest to the garment industry since the faded look and soft feel have great consumer appeal. It is well known to those skilled in the art that the "stone-washed" look and softness of garments can be achieved through agitating the wet garment in contact with pumice stones. U.S. Pat. No. 4,845,790 to Brasington discloses garment treatment techniques in which the use of pumice is combined with the use of bleach.
A number of serious drawbacks are associated with the use of pumice for garment treatment such as: (1) inability to accurately control the abrasion of the garment to achieve the desired "look", (2) lack of consistency in appearance and softness between different batches of treated garments, (3) excessive wear of equipment used for stone washing, (4) requirement for extensive rinse cycles to remove pumice rock from the creases of the garments, (5) need for hand-removal of pumice from the pockets of garments, (6) disposal of abraded pumice. For a description of these well known problems, see, for example U.S. Pat. No. 5,006,126 to Olson et al. Accordingly, extensive efforts have been made to achieve a "stone-washed" effect without the disadvantages associated with the use of pumice rock.
U.S. Pat. No. 5,190,562 to Dickson et al., for example, teaches the preparation and use of a chemical bleaching agent absorbed on an inert carrier (e.g. diatomaceous earth) for denim garment treatment to obtain a faded appearance. The dry powder is tumbled with wet garments, followed by rinsing and drying. While avoiding the use of pumice, the method does not solve the problems of disposal of spent carrier and extensive rinse cycles required to remove carrier from garment seams and pockets. U.S. Pat. No. 5,215,543 to Milora et al. teaches the use of stones for garment abrading in which the stones have a chemical composition that is soluble in rinse water. Compared with the use of pumice this technique is claimed to result in easier removal of the residue from garments and processing equipment. However it does not solve the spent product disposal and equipment abrasion problems.
U.S. Pat. No. 5,213,581 to Olson et al. teaches the use of aqueous cellulase enzyme compositions to provide a "stone-washed" appearance. Use of abrasive or solid materials is completely avoided by this technique. The garment is exposed to a cellulase enzyme composition by agitating the garment in an aqueous solution. The patent discloses that cellulose is removed from the fabric as a result of this treatment. Disadvantages of this type of treatment are: (1) the breakdown of the fabric as a result of cellulose removal (2) the need for stringent control of pH and temperature since the cellulase enzymes work efficiently in a narrow pH and temperature range; and (3) the neutralization and disposal of excess cellulase enzyme compositions present in the fabric and in the excess solution contained in the processing equipment.
Further, aqueous treatment steps such as those employed by Olson and those who use bleaches, pumice or aqueous treatment agents such as dyes, fabric softeners, or permanent press type fabric finishes, are generally carried out through immersion and agitation of the garment in a treatment solution. However, serious disadvantages are associated with any aqueous immersion treatment technique because they require: (1) dilution of treatment agents to prevent excess concentration on random parts of the treated garment leading to uneven or unsightly effects, (2) energy to move or agitate the diluted treatment agent during treatment; and, (3) treatment and/or disposal of treatment agent solution after processing.
U.S. Pat. Nos. 5,235,828 to Aurich et al. and 4,984,317 to Christ teach aqueous textile treatment methods utilizing smaller quantities of liquid to achieve the desired treatment without an excess of treatment agent. Aurich '828 sprays a treatment agent onto lengths of fabric in endless rope form which circulates through a predetermined path in a special treatment chamber. A recirculating liquid jet is used to move the fabric rope and to expose the fabric to the treatment agent. In the Christ '317 patent, fabric is wound on spools and placed in a vessel. A gas stream, containing treatment agent in dispersed form, is forced through the spooled fabric. The gas stream provides the sole force by which treatment agent is applied to the fabric. During treatment, the fabric remains stationary on the spool on which it is stored. The techniques taught by Aurich and Christ may be suitable for processing long lengths of fabric, but these techniques are unsuitable for the treatment of finished garments or small fabric work pieces since these cannot be easily formed into endless rope form or wound onto spools. Further, the practice of the processes taught by Aurich and Christ require special equipment which many clothing manufacturers do not have.
U.S. Pat. No. 4,432,111 to Hoffmann et al. teaches a procedure for washing textiles in a tub-type washing machine using reduced quantities of water compared with conventional textile washing procedures. The tub is driven at a velocity resulting in at least 0.2 g of centrifugal force causing the textiles therein to repeatedly be lifted up and then fall in a trajectory onto the lower portion of the tub. Washing liquid is applied to either the lower portion of the tub, or sprayed into the tub until the textiles are wetted with a quantity of washing liquid equalling 45-100% of the maximum amount which the textiles can absorb. Upon completion of the washing cycle most of the washing liquid is discharged by spinning the inner drum. Rinsing is accomplished in the same manner as washing. The Hoffmann process has the following disadvantages: (1) the process may result in run off of nonabsorbed liquid, thus resulting in a lack of treatment reproducibility between different batches of textiles or non-uniform exposure to treatment agents within a batch, (2) absorption of at least 45% of the maximum which the textiles can absorb resulting in processing inefficiencies to remove the water upon completion of the treatment, and requiring treatment of the waste water, (3) drum velocity resulting in at least 0.2 g centrifugal force compacting the textiles and thus preventing uniform exposure of all textiles surfaces to treatment agent when this is used in small quantities and (4) using a spray which produces a liquid stream which can impact and react with isolated portions of the textiles, producing a non-uniform application of a treatment agent when small quantities of treatment agent are utilized.
Accordingly, the need exists for a treatment technique for garments wherein the desired chemical or physical change can be obtained using conventional equipment without the use of abrasive particles, and with minimal quantities of processing chemicals and water.